Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Ave. S.E.
Washington, D.C. 20590
June 27, 2008
In Reply Refer To: HSSD/B-162B
Mr. Rick Mauer
Nucor Steel Marion Inc
912 Cheney Ave
Marion, Ohio 43302
Dear Mr. Mauer:
This letter is in response to your request for Federal Highway Administration (FHWA) acceptance of a roadside safety system for use on the National Highway System (NHS).
|Name of device/system:||Nu-Guard 31 inch U-post guardrail|
|Type of device/system:||Strong post W-beam barrier|
|Test Level:||NCHRP Report 350 Test Level 4 (TL-4)|
|Testing conducted by:||Holmes Solutions|
|Date of request:||February 15, 2008|
|Date of final package:||April 23, 2008|
You requested that we find this system acceptable for use on the NHS under the provisions of National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended Procedures for the Safety Performance Evaluation of Highway Features.”
Roadside safety systems should meet the guidelines contained in the NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features". FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of July 25, 1997 provides further guidance on crash testing requirements of longitudinal barriers.
The Nucor Steel Marion Nu-Guard 31 inch high strong post W-beam guardrail system consists of standard 12 gauge W-beam attached directly to a 5 pound Nucor modified U post section. The steel line posts are hot rolled steel that is rolled into a U cross section approximately 2 inches deep and 3-1/2 inches wide. The total weight of the posts is 5 pounds per foot. Each post is punched with a 3/4 inch wide slot located 1 inch down from the top of the posts in the middle of the cross section. The slot has a total length of 6-1/2 inches. All posts were 78 inches long and hot dip galvanized.
Washers manufactured from 1/4 inch mild steel plate with an outside diameter of 3-1/2 inches and a 1-inch diameter hole were installed between the guard rail and the legs of the U posts to provide a backing plate to the bolt. The washers have a hot dip galvanized finish. The rail elements are standard 12 gauge BMT (base metal thickness), 350 grade galvanized W-beam, conforming to AASHTO M180 Class A rail. The guardrail system uses standard FBB01 5/8 x 1-1/2 inch galvanized splice bolt and nuts. The W-beams are held to the posts using galvanized 5/8 x 3-1/2 inch bolts with standard FBB01 splice nuts.
Testing for TL-3 had previously been carried out on the Nu-Guard 31 inch W-beam guardrail system to the requirements of Test 3-10 and Test 3-11 from NCHRP 350, these tests being identical to the requirements of Tests 4-10 and 4-11. The results of these tests were documented in Report 5707-07-b and included in FHWA Acceptance Letter B-162 dated September 11, 2007.
Your current request is for TL-4 acceptance and was accompanied by a report documenting testing in standard soil completed in accordance with Test 4-12 from NCHRP 350; using an 8000S (8000 kg) truck traveling at a nominal 80 km/hr and impacting the barrier at the critical impact point at an angle of 15 degrees. The test data summary sheet of this impact is enclosed for reference.
The roadside barrier configuration of the guardrail system contained and redirected the 8000S upright while sustaining moderate damage. The vehicle began to exit before the captured rail caused the vehicle to continue down the length of the barrier, during which time majority of the posts split open at the post bolt slot and separated from the W-beam. No significant debris was expelled from the barrier during the impact, with only plastic components being released from the front of the vehicle. A localized puncture in the face of the guardrail was observed at the point of impact, caused by contact with the truck foot plate. A maximum dynamic deflection of 4 feet was recorded in the barrier. The total length of damage to the barrier caused by the contact of the vehicle was 79 feet, with 5 feet of the damage occurring upstream from the point of impact.
The results of the crash test met the evaluation criteria in the NCHRP Report 350. Therefore, the system described above and detailed in the enclosed drawings is acceptable for use as a TL-3 or 4 system on the NHS under the range of conditions tested, when acceptable to a transportation authority.
Please note the following standard provisions that apply to the FHWA letters of acceptance:
David A. Nicol, P.E.